Plastic bag forming apparatus and method



- 221 Filed v United States Patent [72] Inventor FrancisA.Davis,Jr.

Lansdale, Pennsylvania [21 Appl. No. 726,897

May 6, 1968 Continuation-impart of Ser. No. 664,476, Aug. 30, I967, now Patent No. 3,470,795. Oct. 20, 1970 Paramount Packaging Corp.

Chaliont, Pennsylvania a corporation of Delaware [45] Patented [73] Assignee [54] PLASTIC BAG FORMING APPARATUS AND METHOD ]2 Claims, 10 Drawing F [52] U.S. Cl 93/33, 1 93/35 [51] lnt.C| B31b 1/14 [50] Field olSearch 156/251;

93/8, 33, 33(H), 35, 35(RB); (Heat Seal Digest) [56] References Cited 7 UNITED STATES PATENTS 3,111,874 11/1963 Groveretal x3/155x 3,395,622 8/1968 Kugler 93/33x FOREIGN PATENTS 684,890 12/1952 GreatBritain....1 0. 93/35 1,040,439 8/1966 GreatBritain 93/33 Primary Examiner-H. A. Kilby, .lr. Attorney-Seidel, Gonda and Goldhammer ABSTRACT: Apparatus and method are disclosed for making open-gusset bags from thermoplastic material. Reciprocating blades are disposed within the gusset of a continuous web. The blades are used to open the gusset after a generally V-shaped notch is removed from the gusset and before the web is divided into bags. One gusset half may be flipped over before the final cutting ofthe web into side-welded bags.

Sheet um/M ATTORNEYS.

Sheet R m w N FRANCIS A. DA V/S, JR.

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Patented Oct. 20, 1970 3,534,665

Sheet 3 of 4 INVENTO i FRANCIS A. DA V/S, JR.

ATTORNEYS- Patented Oct. 20, 1970 3,534,665

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ATTORNEYS.

PLASTIC BAG FORMING APPARATUS AND METHOD This application is a continuationdn-part of my pending application Ser. No. 664,476 filed on Aug. 30, 1967 now U.S. Pat. No. 3,470,795 and entitled Method and Apparatus for Making Plastic Bags. The disclosure therein is incorporated herein by reference.

When a web of thermoplastic material is folded so that it can overlie itself and has a longitudinally extending foldline, there are two layers of material, namely a top and bottom layer. When a gusset is formed along the foldline, in the gusset there will be four layers of overlapping material. When a notch is cut through the gusset by a welder, the top two layers are welded together and the bottom two layers are welded together along the notch. The second and third layers do not weld together since they are coated with a heat-resistant material or heat-resistant ink. However, there is a tendency of the second and third layers to stick together.

When the bag is filled with merchandise, or opened by introducing air under pressure into the bag, some of the gussets do not fully open due to the sticking of the second and third layers at the gusset. The apparatus and method of the present invention is directed to separating the second and third layers of the gusset immediately after the notch weld is formed. As a result thereof, the frequent occurrence of the gusset failing to open during filling as referred to above is eliminated. In addition, the present invention may include means for folding onehalf of the gusset over the bag body so as to reduce the thickness at the gusset end of a stack of bags.

It is an object of the present invention to provide novel apparatus and method for forming open gusset bags from thermoplastic material.

It is another object of the present invention to provide apparatus and method for making notches defined by seam welds at a gusset or folded thermoplastic material and opening the gusset before the material is transversely cut at the apex of the notches so as to form side-welded bags.

It is another object of the present invention to provide apparatus and method for making open gusset side-welded thermoplastic bags with one-half of the gusset folded over the bag body.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a top plan view of the apparatus of the present invention;

FIG. 2 is a view taken along the line 2-2 in FIG. 1;

FIG. 3 is a view taken along the line 33 in FIG. 2;

FIG. 4 is a view taken along the line 4-4 in FIG. 2;

FIG. 5 is a view taken along the line 5-5 in FIG. 4;

FIG. 6 is a partial perspective view of the gusset portion of the web with the blades disposed within the gusset;

FIG. 7 is a partial perspective view of the notched web with a portion of the gusset being turned over;

FIGS. 8 and 9 are diagrammatic illustrations of the manner in which the gusset is turned over; and

FIG. 10 is a partial perspective view of a corner of a bag made in accordance with the present invention.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIG. I a bag making apparatus of the present invention designated generally as 10. Apparatus 10 is intended to have fed therethrough a pair of spaced parallel thermoplastic webs 12 and 14. Thus, the apparatus 10 has two parallel production lines, each defined by one of the webs. The webs l2 and 14 are processed in the same manner.

The web 12 is folded along foldline 16 so that the web overlies itself. Web 14 is similarly-folded along line 18. Since each of the webs l2 and 14 are treated in the same manner, only web 12 will be described in detail. It will be understood that corresponding structure is illustrated, at least in part, in conjunction with web 14.

From large rolls, the web 12 is unwound and fed through a take-up roll assembly 24. When forming foldline 16, the top layer 20 and bottom layer 22 overlie one another so as to provide a protruding edge portion 23 on the bottom layer 22.

5 Along the web 12, there are printed markers for breaking the beam of photocell units which intermittently operate the apparatus l0.

Along the foldline 16, there is provided a rotatable gusset plate 26 which forms a gusset along the foldline. A similar gusset plate 28 is provided for web I4. The gusset plates as well as the apparatus specifically described so far may be of the type as disclosed in U.S. Pat. No. 3,282,173.

The gusseted web is then fed so that the protruding edge portion 23 may be provided with perforations or slits by means of the slitter 30. A similar slitter 32 is provided for web 14. The slitter may be of the type shown in U.S. Pat. No. 3,183,750 which is useful for producing guides of the type shown in U.S. Pat. No. 3,184,055. I

Thereafter, the web 12 is fed to intermittently operated notch welder 34. The notch welder 34 is adapted to cut notches 36 from the gusset at spaced points thercalong. When forming the notches 36, the top layer of thermoplastic material 20 is welded to the second layer of material 40 along weld line 38. Simultaneously, the bottom layer 22 is welded to the third layer 44 along weld line 42.

The notch 36 is defined by converging lines 39 and 41. The layers 40 and 44 tend to stick together along lines 39 and 41. Because of a heat resisting chemical or ink applied to the juxtaposed surfaces on layers 40 and 44, these two layers do not weld together. In order to open the gusset along lines 39 and 41, there is provided a pair of blades 46 and 48.

Blades 46 and 48 are adapted to move toward and away from each other. Initially, the blades 46 and 48 are spaced from one another when the notch 36 is made. Thereafter, the blades reciprocate towards each other to separate the layers 40 and 44 from each other along the lines 39 and 41. At all times, the blades 46 and 48 lie in a horizontal plane and extend into the space between layers 40 and 44.

Referring to FIG. 2, it will be noted that the web 12 is not shown therein since it would render the figure more complicated and tend to obscure the disclosure. In FIG. 2, the web will be moving from right to left. At its left-hand end, the blade 48 is provided with a perforated manifold conduit 57 connected to flexible conduit 59. Conduit 57 lies in the plane of blade 48. The blade 48 is supported at its right-hand end by a bracket 60. The upper end of bracket 60 is connected to a piston rod 62. The piston rod 62 is connected to a piston disposed within cylinder 64. Conduits are provided for introducing pressurized air into the cylinder 64 to cause reciprocation of the blade 48.

A rack 66 is connected to the upper end of bracket 60. Rack 66 meshes with pinion 68. See FIGS. 2 and 3. Pinion 68 is in meshing engagement with a rack 70. Rack 70 is below and parallel to rack 66. Rack 70 is connected to a bracket 72. The lower end of bracket 72 is connected to the blade 46. The right-hand end of blade 46 is provided with a perforated conduit 65 similar to conduit 57 on the front edge of blade 48. Conduit 65 has a flexible conduit 67.

The bracket 60 is provided with a T-shaped member disposed within a corresponding shaped slot 74 on guide member 79. As shown more clearly in FIG. 3, bracket 72 is provided with a similar T-shaped member 78 disposed within a T-shaped slot 76 on guide member 80. The members 79 and 80 guide the brackets 60 and 72.

The notch welder 34 includes a die head 82 which is generally V-shaped. See FIGS. 4 and 5. An electric heating element 84 is provided within the die head 82 to heat the same to the desired temperature, whereby the layers will be cut and welded along lines 39 and 41. Die head 82 is provided with a V-shaped cutting edge 86. A pressure plate 88 having a coolant conduit 90 therein is attached to the die head 82. The cooled pressure plate limits the extent of heat transfer only to the immediate area of the lines 39 and 41.

The die head 82 and pressure plate 88 are supported from a platen 92 thereabove by means of rods 94. Rods 94 are preferably made from low heat transmitting materials or heat insulating materials. Platen 92 is provided with an actuating rod 96 extending upwardly therefrom (See FIGS. 2 and 3).

The rod 96 extends through a bushing 98 and is connected at its upper end to a boss 100 on ring 102. Ring 102 is rotatably supported by an eccentric 104 mounted on shaft 106. As shaft 106 rotates, the cooperation between eccentric 104 and ring 102 causes the rod 96 to reciprocate up and down.

On shaft 106, there is also mounted a plate 108 having a follower 110 adjacent its periphery. The follower 110 is coupled to a geneva intermittent drive mechanism 112 which in turn intermittently drives chain 114. Chain 114 is coupled through meshing beveled gears 116 to the roller 52 so that the belt 50 is intermittently driven.

Belt 50 extends around driven roller 52, idler rollers 54, and a take-up idler roller 56. The vertical disposition of roller 56 may be adjusted by means of screw 58 (See FIG. 3). The axis of the rollers 5256 is parallel to the direction of the movement of the web. Hence, the belt 50 moves transversely to the direction of the web for a purpose to be described hereinafter.

Referring to FIG. 3, there is provided a cylinder 118 on the platen 92. A piston rod 120 extending from the cylinder 118 terminates at its free end in a resilient finger 122 which is curved between its upper and lower end so that it may collapse on itself. Introduction of pressurized air into opposite ends of the cylinder 118 results in reciprocation of the piston rod 120 and finger 122 in the direction of movement of the belt 50, which is transverse to the direction of movement of the web 12.

Referring to FIG. 1, the notched web 12 is cut into individual side-welded bags 126 by means of a welder 124 which cuts the web 12 transversely at spaced points therealong corresponding to the apex of the notches 36. As shown in FIG. 1, the gussets on the bags 126 are not only open but one-half of the gusset has been folded back over the body of the bag. This may be accomplished as follows.

The notched web having welds along the lines 39 and 41 at spaced points along the web is shown diagrammatically in FIG. 8 in order to cause the top half of the gusset to move from the disposition shown in FIG. 8 where it overlies the other gusset half to a position as shown in FIG. 9 wherein it overlies the body, the blade 46 may be provided with a plow 128 which lifts the top gusset half upwardly so that it is generally vertically disposed. Thereafter, a stationary plow 130 flattens out the top gusset half so that it overlies the body ofthe bag (See FIGS. 3, 4 and 7-9).

The apparatus 10 is utilized as follows:

The first step in practicing the invention is to feed the webs 12 and 14 of thermoplastic sheet material overlapped on themselves so as to have adjacent foldlines 16 and 18. The following description will relate only to web 12 since it is possible to process only one web. It will be understood that the same steps are applied to web 14. The rotating plate 26 forms a gusset at the foldline 16. The drive mechanism for the apparatus 10 is intermittently operated in any convenient manner such as by the photoelectric cells 132 which detect markings on the web 12. Other well-known control means for intermittent operation may be used. While web 12 is stationary, the following occur generally simultaneously: slitting the edge portion 23 by slitter 30, cutting the notch 36 along lines 39 and 41 and effecting the welds 38 and 42, separating the gusset halves, removing the V-shaped tab, and cutting the web 12 into bags 126 along the apex of a previously formed notch by means of welder 124. Immediately thereafter, the web 12 is indexed for another bag width.

The welder 34 is synchronized by shaft 106 which in turn is synchronized with welder 124 and slitter 30. As shaft 106 rotates, the die head 82 is reciprocated towards the gusset. The finger 122 contacts the gusset at the area which will be the cut tab and is flexed so as to press the tab against the belt 50. The cutting edge 86 cuts the notch 36. Simultaneously with cutting the notch, the layers 20 and 40 are welded together along seam weld 38 and layers 22 and 44 are welded together along seam weld 42. The layers 40 and 44 tend to stick together along lines 39 and 41.

Immediately thereafter, and before the web 12 has started moving again, pressurized air is introduced into cylinder 118 to move the piston rod 120 to the left in FIG. 3. Simultaneously, the belt 50 will be caused to move to the left in FIG. 3 by means of the geneva drive mechanism 112. Thus the cut tab is moved away from the gusset while held against belt 50 by finger 122. Movement of finger 122 and belt 50 is simultaneous.

Introduction of pressurized air into cylinders 64 and 118 is controlled by cams on shaft 106 which cooperate with microswitchesAs soon as the tab has been removed, die head 82 moves upwardly and pressurized air is introduced into cylinder 64 to reciprocate the blades 46 and 48 toward one another. Since the blades 46 and 48 are disposed in the gusset between layers 40 and 44, they separate these layers along line 39 and 41 as they move toward one another. This separation is effected by a combination of mechanical and air pressure action. Air under a pressure of about 10 p.s.i.g. is continuously directed from perforations in conduits 57 and 65 parallel to foldline 16. Just before contact is made with line 39 and 41, the air is trapped in a triangular pocket in the gusset to assist in separating the gusset halves.

Thereafter the web 12 is moved to the right in FIG. 1 for a distance corresponding to one bag width. If plows 128 and 130 are provided, the top gusset half (layers 20 and 40) will be flipped over so as to overlie the bag body portion of the web before the welder I24 cuts the web 12 transversely into individual side-welded bags 126.

As pointed out above, the heat resistant ink on layers 40 and 44 prevents these layers from being welded to each other. If these layers are not printed, a heat resistant chemical such as a varnish may be applied to the surfaces of these layers. Instead, it is also possible to merely oxidize the surfaces of the polyethylene material in the area of the gusset to prevent layers 40 and 44 from welding together.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

Iclaim:

1. A method of making bags from thermoplastic material comprising the steps of providing a web of material having top and bottom layers, forming a gusset along the fold lines so as to have four layers of material in overlapping relation at the gusset, cutting generally V-shaped notches at spaced points along the gusset and simultaneously seam welding edges of the notches, removing the cut tab at the location where the notches are cut and before moving the web of material, separating the top half of the gusset from the bottom half of the gusset at the edges of the notches after the edges of the notches have been welded by moving at least one blade along the gusset at the zone of the notches, moving the web of material, and then transversely cutting the web into sidewelded bags at locations corresponding to the apex of the notches.

2. A method in accordance with claim 1 wherein said step of separating the top and bottom halves of the gusset includes locating a pair of blades in a plane between the top and bottom halves of the gusset, said step of cutting the notches being done in a location which is between the adjacent ends of the blades, and then moving the blades towards each other to perform said separating step.

3. A method in accordance with claim 1 including the step of folding upwardly the top gusset half so that it lies in a generally horizontal plane overlying a body portion of the web before the web is cut transversely to form the side welds of the bag.

4. A method in accordance with claim 1 wherein said step of removing the cut tab includes supporting the gusset on a conveyor, and then moving the conveyor transversely of the web after the notch has been cut for transporting the cut tab away from the notch.

5. Apparatus for making bags of thermoplastic material comprising means for longitudinally overlapping the material on itself and providing a gusset at the fold line, a notch welder for cutting notches at spaced points along the gusset and simultaneously providing a first V-shaped seam weld between the uppermost layer and the second layer and a second V- shaped seam weld between the third and bottom layers, means movable along the gusset for separating the second and third layers at the periphery of the notches before the material is cut transversely into individual bags, said separator means including a pair of blades disposed in the gusset between the second and third layers, means for selectively moving the blades along the gusset toward and away from one another, and means for removing the tabs produced by cutting the notches.

6. Apparatus in accordance with claim 5 wherein said motor means is connected to one of the blades for reciprocating the same, and mechanical means interconnecting the blades so that the blades reciprocate in opposite directions.

7. Apparatus in accordance with claim 5 including a belt disposed beneath the notch welder, and means for moving the belt in a direction away from the gusset after a notch has been cut.

8. Apparatus in accordance with claim 5 including a plow means for folding a top gusset half about the foldline through an arc of approximately 180 after said welds have been made.

9. Apparatus in accordance with claim 5 including air discharge means at the leading edge of each blade for directing pressurized air in the direction of the other blade, and flexible conduits connected to each air discharge means.

10. Apparatus in accordance with claim 5 wherein said notch welder for cutting notches includes a die head provided with a V-shaped cutting edge, and a motor means for reciprocating the die head downwardly toward the material to effect the V-shaped seam weld between the uppermost layer and the second layer and for moving the die head away from said material.

11. Apparatus in accordance with claim 10 including a water-cooled pressure plate of the same general configuration as said die head, and means mounting said die head and pressure plate for simultaneous movement as a unit, said pressure plate being of greater size than said cutting edge and being adjacent thereto to limit the extent of heat transfer in said material.

12. Apparatus for making bags of thermoplastic material comprising means for longitudinally overlapping the material on itself and providing a gusset at the foldline, a notch welder for cutting notches at spaced points along the gusset and simultaneously providing a first V-shaped seam weld between the uppermost layer and the second layer and a second V- shaped seam weld between the third and bottom layers, means for separating the second and third layers at the periphery of the notches before the material is cut transversely into individual bags, said notch welder including a V-shaped head mounted on support structure, means for reciprocating the structure and die head in a vertical direction, said die head including a water-cooled pressure plate of the same general configuration, said support structure including a finger adapted to overlie and contact the cut tab, motor means for reciprocating the finger in a direction away from the gusset, a conveyor below the die head for cooperation with the finger, means for moving the conveyor in the same direction at the same time as the finger moves, and means for removing the tabs produced by cutting the notches. 

